Match the functions in Table 1 with the keys in Table 2.
Table 1
a to encrypt a message for sending
b to decrypt a received message
c to encrypt the MAC of a message
d to encrypt the MAC of a digital signature
Table 2
i sender's private key
ii trusted issuer's private key
iii the recipient's private key
iv the recipient's public key
Match the terms in Table A with the statements in Table B.
| a | Gibberish |
| b | Impostor |
| c | Decipher |
| d | MAC |
| e | Tenets |
| f | Tamper |
Table B
i Message-authentication code
iiPrincipal features
iiiMeaningless data
iv Person pretending to be someone else
vMake unauthorised changes
vi Convert to meaningful data
Text 13
I. Find the answers to these questions in the following text.
1. Name 3 areas of computing that companies rely on more and more.
2. What can intimidate even the most experienced network manager?
3. What 3 types of peripheral storage devices do most companies rely on for backing up data and storing information?
4. What type of data-intensive application do companies rely more heavily on?
5. What has kept the SCSI bus from evolving rapidly?
6. What traditional LAN interface is mentioned in the text?
7. Name 2 drawbacks of NAS.
8. What type of server can be connected to a SAN?
9. In what 2 ways will a SAN lighten your server's workload?
10. What types of cabling can be used with Fibre Channel?
Doing the SAN thing
As companies rely more and more on ecommerce, online-transaction processing and databases, the amount of information that needs to be managed and stored on a network can intimidate even themost experienced of network managers.
While servers do a good job of storing data, their capacity is limited and they can become a bottleneck if too many users try to access the same information. Instead, most companies rely on peripheral storage devices, such as tape libraries. RAID disks and even optical storage systems. These devices are effective for backing up data online and storing large amounts of information.
But as server farms increase in size and companies rely more heavily on data-intensive applications, such as multimedia, the traditional storage model isn't quite as useful. This is because access to these peripheral devices can be slow, and it might not always be possible for every user to easily and transparently access each storage device.
The most basic way of expanding storage capacity on the network is to hang disk arrays or other storage devices off servers, using the SCSI interface or bus.
While SCSI has been a workhorse over the years for connecting peripherals at a relatively fast speed, distance limitations have kept this particular bus interface from evolving rapidly.The SCSI standards put a bus length limit of about 6m on devices. While this distance limitation doesn't really affect connecting storage devices directly to a server, it does severely restrict placing RAID and tape librariesat other points on the network.
Enter the NAS
This is where the concept of Network Attached Storage (NAS) comes in. NAS is simple in concept and execution: disk arrays and other storage devices connect to the network through a traditional LAN interface, such as Ethernet. Storage devices would thus attach to network hubs, much the same as servers and other network devices. However, NAS does have a few drawbacks.
First, network bandwidth places throughput limitations on the storage devices. Another downside to NAS is the lack of cohesion among storage devices. While disk arrays and tape drives are on the LAN. managing the devices can prove challenging, since they are separate entities and not logically tied together. NAS has its place as a viable storage architecture, but large companies need something more.
Mr SAN man
Large enterprises that want the ability to store and manage large amounts of information in a high-performance environment now have another option: the Storage Area Network (SAN). In a SAN, storage devices such as Digital Linear
Tapes (DLLs) and RAID arrays are connected to many kinds of servers via a high-speed interconnection, such as Fibre Channel.
This high-speed link creates a separate, external network, that's connected to the LAN, but acts as an independent entity.
This setup allows for any-to-any communication among all devices on the SAN. It also provides alternative paths from server to storage device. In other words, if a particular server is slow or completely unavailable, another server on the SAN can provide access to the storage device. A SAN also makes it possible to mirror data, making multiple copies available.
SANs offer several advantages. First, they allow for the addition of bandwidth without burdening the main LAN. SANs also make it easier to conduct online backups without users feeling the bandwidth pinch. When more storage is needed, additional drives do not need to be connected to a specific server; rather, they can simply be added to the storage network and accessed from any point.
Another reason for the interest in SANs is that all the devices can be centrally managed. Instead of managing the network on a per-device basis, storage can be managed as a single entity, making it easier to deal with storage networks that could potentially consist of dozens or even hundreds of servers and devices.
You can connect almost any modern server to a SAN, because SAN-support hardware and software spans most PC midrange and mainframe platforms. Ideally, a SAN will lighten your server's workload by offloading many storage-related server tasks to the SAN and by better allocating storage resources to servers.
The most important piece of any SAN architecture is the underlying network technology that drives it. You can use ordinary Fast Ethernet, but Fibre Channel is emerging as the technology of choice for SAN implementations. Fibre Channel was developed by ANSI in the early 1990s as a means to transfer large amounts of data very quickly. Fibre Channel is compatible with SCSI, IP, IEE 802.2, ATM Adaptation Layer for computer data,and Link Encapsulation, and it can be used over copper cabling or fibre-optic cable.
II. Re-read the text to find the answers to these questions.